/* ------------------------------------------------------------------
   Qingyu Meng — personal site
   ------------------------------------------------------------------ */

/* Light is the default for everyone, whatever the operating system is set to.
   Dark applies only after the reader presses the toggle in the header, which
   pins data-theme="dark" on <html>. */

:root {
  color-scheme: light;

  --bg: #ffffff;
  --bg-soft: #f6f8fa;
  --ink: #333;
  --ink-soft: #586069;
  --ink-faint: #6a737d;
  --ink-disabled: #9aa0a6;
  --link: #4183c4;
  --key: #41489b;
  --key-bg: #ecedfa;
  --rule: #eee;
  --rule-strong: #d1d5da;

  --tag: #3a87ad;
  --tag-muted: #6a737d;
  --tag-ink: #fff;

  --chip5-ink: #1b4f72;
  --chip5-bg: #eaf1f8;
  --chip5-line: #cfe0ef;

  --kw-a: #a3342a;
  --kw-b: #6c3a9e;
  --kw-c: #0e7263;
  --kw-d: #a05a08;
  --kw-e: #1a5fa8;
  --kw-f: #2c7a3f;
  --kw-g: #a02f61;
}

:root[data-theme="dark"] {
  color-scheme: dark;

  --bg: #0d1117;
  --bg-soft: #161b22;
  --ink: #e6edf3;
  --ink-soft: #9198a1;
  --ink-faint: #7d8590;
  --ink-disabled: #6e7681;
  --link: #4493f8;
  --key: #b5b9f0;
  --key-bg: #191b33;
  --rule: #30363d;
  --rule-strong: #484f58;

  --tag: #316dca;
  --tag-muted: #545d68;
  --tag-ink: #fff;

  --chip5-ink: #a5d6ff;
  --chip5-bg: #0f2439;
  --chip5-line: #1f3f5f;

  --kw-a: #ff7b72;
  --kw-b: #d2a8ff;
  --kw-c: #56d4c0;
  --kw-d: #ffa657;
  --kw-e: #79c0ff;
  --kw-f: #7ee787;
  --kw-g: #ff9bce;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: Georgia, Avenir, Rockwell, SimSun, FZKai-Z03S, Helvetica, Tahoma, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--ink);
  background: var(--bg);
  word-wrap: break-word;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--link); text-decoration: none; }
a:hover { text-decoration: underline; }

:focus-visible {
  outline: 2px solid var(--link);
  outline-offset: 2px;
  border-radius: 2px;
}

h1, h2, h3 { text-wrap: balance; }

img { max-width: 100%; }

hr {
  height: 0;
  margin: 24px 0;
  border: 0;
  border-bottom: 1px solid var(--rule);
}

.container {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 16px;
}

/* --- header ------------------------------------------------------- */

.site-header {
  padding: 20px 0;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--rule);
}

.site-header .container {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px 18px;
}

.site-header h1 {
  margin: 0 auto 0 0;
  font-size: 30px;
  font-weight: 400;
  line-height: 1.2;
}

.site-header h1 a { color: var(--ink); }
.site-header h1 a:hover { text-decoration: none; }

.site-header h1 .ipa {
  color: var(--ink-soft);
  font-size: 0.6em;
  white-space: nowrap;
}

.site-header-nav { order: 2; display: flex; flex-wrap: wrap; gap: 18px; }

.site-header-nav a {
  font-size: 14px;
  color: var(--ink);
}

.site-header-nav a.is-current {
  font-weight: 700;
  border-bottom: 2px solid var(--link);
}

.nav-toggle {
  display: none;
  padding: 6px 10px;
  font: inherit;
  font-size: 14px;
  color: var(--ink);
  background: var(--bg);
  border: 1px solid var(--rule-strong);
  border-radius: 3px;
  cursor: pointer;
}

.header-tools {
  order: 3;
  display: flex;
  align-items: center;
  gap: 10px;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 30px;
  height: 30px;
  padding: 0;
  color: var(--ink-soft);
  background: none;
  border: 1px solid transparent;
  border-radius: 4px;
  cursor: pointer;
}

.theme-toggle:hover {
  color: var(--ink);
  border-color: var(--rule-strong);
}

.theme-toggle svg {
  display: block;
  width: 17px;
  height: 17px;
  fill: currentColor;
}

/* moon while the page is light (click for dark), sun while it is dark */
.theme-toggle .icon-sun { display: none; }

:root[data-theme="dark"] .theme-toggle .icon-moon { display: none; }
:root[data-theme="dark"] .theme-toggle .icon-sun { display: block; }

/* --- two-column layout -------------------------------------------- */

.columns {
  display: flex;
  flex-wrap: wrap;
  gap: 0 4%;
  align-items: flex-start;
}

.column-main { flex: 1 1 62%; min-width: 0; }
.column-side { flex: 1 1 30%; min-width: 0; }

.column-side.is-sticky {
  position: sticky;
  top: 24px;
}

/* --- prose -------------------------------------------------------- */

.prose > *:first-child { margin-top: 0; }

.prose h2 {
  margin: 32px 0 12px;
  padding-bottom: 6px;
  font-size: 22px;
  font-weight: 700;
  line-height: 1.3;
  border-bottom: 1px solid var(--rule);
}

.prose h3 {
  margin: 24px 0 8px;
  font-size: 17px;
  font-weight: 700;
  line-height: 1.3;
}

.prose p { margin: 0 0 14px; }

.prose ul { margin: 0 0 14px; padding-left: 22px; }
.prose li { margin-bottom: 6px; }

/* bullet-less lists sit flush with the headings above them */
.prose .pub-list,
.prose .thesis-list,
.prose .timeline { padding-left: 0; }

.lede {
  margin-bottom: 18px;
  line-height: 1.55;
}

.lede .org { display: block; }

.intro {
  margin: 20px 0 4px;
  line-height: 1.7;
}

.quote {
  margin: 52px 0 0;
  padding: 4px 0 4px 20px;
  color: var(--ink-soft);
  font-size: 19px;
  line-height: 1.65;
  font-style: italic;
  border-left: 3px solid var(--rule);
}

.quote p { margin: 0 0 14px; }

.quote cite {
  display: block;
  margin-top: 12px;
  font-size: 16px;
  font-style: normal;
}

.note { color: var(--ink-soft); font-size: 14px; }

/* keyword accents in the research-interest list */
.kw { font-weight: 700; }
.kw-a { color: var(--kw-a); }
.kw-b { color: var(--kw-b); }
.kw-c { color: var(--kw-c); }
.kw-d { color: var(--kw-d); }
.kw-e { color: var(--kw-e); }
.kw-f { color: var(--kw-f); }
.kw-g { color: var(--kw-g); }

/* --- publications -------------------------------------------------- */

.pub-list { margin: 0; padding: 0; list-style: none; }

.pub-list > li { margin-bottom: 20px; }

/* line 1: venue-and-ranking pill, then the title */
.pub-head { margin: 0 0 1px; line-height: 1.5; }

.pub-tag {
  display: inline-block;
  /* measured width of the longest key, so every title starts at the same column */
  min-width: 190px;
  margin-right: 9px;
  padding: 1px 11px;
  font: 700 11px/19px Helvetica, Arial, sans-serif;
  letter-spacing: 0.03em;
  color: var(--key);
  text-align: center;
  white-space: nowrap;
  vertical-align: baseline;
  background: var(--key-bg);
  border-radius: 999px;
}

.tag-venue { font-size: 13px; }

.pub-title { font-weight: 700; }

/* line 2: authors */
.pub-authors { margin: 0 0 1px; line-height: 1.5; }
.pub-authors .me { font-weight: 700; }

/* line 3: venue, its ranking, then the links */
.pub-where {
  margin: 0;
  color: var(--ink-soft);
  line-height: 1.5;
}

.pub-where strong { color: var(--ink); font-weight: 700; }

.pub-links { margin-left: 8px; }

.pub-links a,
.pub-links .soon {
  margin-left: 6px;
  font-family: Helvetica, Arial, sans-serif;
  font-size: 13px;
  white-space: nowrap;
}

.pub-links .soon { color: var(--ink-disabled); }

.pub-summary {
  margin: 3px 0 0;
  color: var(--ink-soft);
  font-size: 14.5px;
  line-height: 1.55;
}

/* --- thesis supervision --------------------------------------------- */

.thesis-list { margin: 0; padding: 0; list-style: none; }

.thesis-list > li { margin-bottom: 16px; }

.thesis-name { font-weight: 700; }

.thesis-meta {
  color: var(--ink-soft);
  font-size: 14.5px;
}

.thesis-meta::before { content: "\00a0\00b7\00a0"; }

.thesis-title {
  display: block;
  font-style: italic;
}

/* --- timeline (education / experience) ----------------------------- */

.timeline { margin: 0; padding: 0; list-style: none; }

.timeline > li {
  display: flex;
  flex-wrap: wrap;
  gap: 0 14px;
  margin-bottom: 14px;
}

.timeline .when {
  flex: 0 0 142px;
  color: var(--ink-soft);
  font-family: Helvetica, Arial, sans-serif;
  font-size: 13.5px;
  line-height: 1.75;
}

.timeline .what { flex: 1 1 240px; min-width: 0; }
.timeline .what strong { font-weight: 700; }
.timeline .where { color: var(--ink-soft); }
.timeline .detail { color: var(--ink-soft); font-size: 14.5px; }

/* --- skills / languages -------------------------------------------- */

.skill-group { margin-bottom: 12px; }

.skill-group .skill-label {
  display: inline-block;
  min-width: 132px;
  padding-right: 10px;
  font-weight: 700;
  vertical-align: top;
}

.chip {
  display: inline-block;
  margin: 0 4px 5px 0;
  padding: 1px 8px;
  font-family: Helvetica, Arial, sans-serif;
  font-size: 12.5px;
  line-height: 18px;
  color: var(--ink-soft);
  background: var(--bg-soft);
  border: 1px solid var(--rule);
  border-radius: 3px;
}

.chip.lv5 { color: var(--chip5-ink); background: var(--chip5-bg); border-color: var(--chip5-line); }

/* --- sidebar ------------------------------------------------------- */

.widget { margin-bottom: 26px; }

.widget h3 {
  margin: 0 0 10px;
  padding-bottom: 6px;
  font-size: 17px;
  font-weight: 700;
  border-bottom: 1px solid var(--rule);
}

.profile-avatar {
  display: block;
  width: 62%;
  aspect-ratio: 1 / 1;
  margin: 0 auto 12px;
  object-fit: cover;
  object-position: 50% 50%;
  border: 1px solid var(--rule-strong);
  border-radius: 50%;
}

.profile-name {
  text-align: center;
  font-weight: 700;
}

.profile-title {
  margin-top: 6px;
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.45;
  text-align: center;
}

.contact-list { margin: 0; padding: 0; list-style: none; }

.contact-list li { margin-bottom: 8px; }

.contact-list a,
.contact-list span {
  display: flex;
  align-items: center;
  gap: 9px;
  font-size: 14px;
  line-height: 1.4;
}

.contact-list span { color: var(--ink-soft); }

.contact-list svg {
  flex: 0 0 16px;
  width: 16px;
  height: 16px;
  fill: var(--ink-soft);
}

.news-item {
  margin: 0 0 10px;
  font-size: 14.5px;
  line-height: 1.5;
}

.label {
  display: inline-block;
  margin-right: 4px;
  padding: 2px 5px;
  font-family: Helvetica, Arial, sans-serif;
  font-size: 11.5px;
  font-weight: 700;
  line-height: 14px;
  color: var(--tag-ink);
  white-space: nowrap;
  vertical-align: 1px;
  background: var(--tag);
  border-radius: 2px;
}

/* --- gallery -------------------------------------------------------- */

.album { margin-bottom: 40px; }

.album h2 {
  margin: 0 0 4px;
  padding-bottom: 6px;
  font-size: 22px;
  font-weight: 700;
  border-bottom: 1px solid var(--rule);
}

.album-subtitle {
  margin: 0 0 14px;
  color: var(--ink-soft);
  font-size: 15px;
  font-style: italic;
}

.album-note {
  margin: 14px 0 0;
  color: var(--ink-soft);
  font-size: 15px;
}

.masonry { column-gap: 12px; }
.masonry-3 { column-count: 3; }
.masonry-2 { column-count: 2; }

.masonry a {
  display: block;
  margin: 0 0 12px;
  break-inside: avoid;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}

.grid-2 a { display: block; }

.grid-2 img {
  width: 100%;
  height: 220px;
  object-fit: cover;
}

.masonry img,
.grid-2 img {
  display: block;
  border: 1px solid var(--rule);
  border-radius: 3px;
  transition: opacity 0.15s ease;
}

.masonry img { width: 100%; }

.masonry a:hover img,
.grid-2 a:hover img { opacity: 0.85; }

/* --- lightbox -------------------------------------------------------- */

.lightbox {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 40px 60px;
  background: rgba(0, 0, 0, 0.9);
}

.lightbox.is-open { display: flex; }

.lightbox img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
}

.lightbox-btn {
  position: absolute;
  padding: 0;
  font: 400 34px/1 Helvetica, Arial, sans-serif;
  color: #fff;
  background: none;
  border: 0;
  cursor: pointer;
  opacity: 0.7;
}

.lightbox-btn:hover { opacity: 1; }

.lightbox-close { top: 12px; right: 18px; font-size: 40px; }
.lightbox-prev { left: 14px; top: 50%; transform: translateY(-50%); }
.lightbox-next { right: 14px; top: 50%; transform: translateY(-50%); }

.lightbox-caption {
  position: absolute;
  bottom: 14px;
  left: 0;
  right: 0;
  font-family: Helvetica, Arial, sans-serif;
  font-size: 13px;
  color: #ccc;
  text-align: center;
}

/* --- footer ---------------------------------------------------------- */

.site-footer {
  margin-top: 44px;
  padding: 18px 0 34px;
  border-top: 1px solid var(--rule);
  color: var(--ink-faint);
  font-size: 13.5px;
}

.site-footer .container {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 16px;
  justify-content: space-between;
}

/* --- responsive ------------------------------------------------------ */

@media (max-width: 900px) {
  .timeline .when { flex-basis: 100%; }
}

@media (max-width: 768px) {
  body { font-size: 15.5px; }

  .site-header .container { align-items: center; }
  .site-header h1 { font-size: 24px; }

  .nav-toggle { display: block; }

  .site-header-nav {
    order: 4;
    display: none;
    flex-basis: 100%;
    flex-direction: column;
    gap: 0;
    margin-top: 10px;
    border-top: 1px solid var(--rule);
  }

  .site-header-nav.is-open { display: flex; }

  .site-header-nav a {
    padding: 9px 2px;
    border-bottom: 1px solid var(--rule);
  }

  .site-header-nav a.is-current { border-bottom: 1px solid var(--rule); }

  .columns { flex-direction: column-reverse; gap: 0; }

  .column-main,
  .column-side { flex-basis: 100%; width: 100%; }

  .column-side.is-sticky { position: static; }

  .column-side { margin-bottom: 26px; }


  .profile-avatar { width: 112px; }

  .widget { margin-bottom: 20px; }
  .contact-list li { margin-bottom: 6px; }

  .masonry-3 { column-count: 2; }

  .lightbox { padding: 50px 14px; }
  .lightbox-prev { left: 4px; }
  .lightbox-next { right: 4px; }
}

@media (max-width: 480px) {
  .masonry-3, .masonry-2 { column-count: 1; }
  .grid-2 { grid-template-columns: 1fr; }
  .grid-2 img { height: 200px; }
  /* on a narrow screen the key sits on its own line above the title */
  .pub-tag { min-width: 0; margin-right: 0; }
  .pub-head .pub-title { display: block; margin-top: 4px; }
  .skill-group .skill-label { display: block; margin-bottom: 4px; }
}